[Docs] unify scrim opacity

Nobody has claimed this yet.

**Description:** #3635
- https://m3.material.io/styles/elevation/applying-elevation:
```
Scrims use the scrim color role at an opacity of 32%.
```
- https://m3.material.io/components/navigation-drawer/specs:
```
Navigation drawers scrim color md.ref.palette.neutral-variant20
Navigation drawers scrim opacity 0.4
```
- https://github.com/material-components/material-components-android/blob/master/docs/components/NavigationDrawer.md:
```
Element | Attribute | Related method(s) | Default value
Color | N/A | setScrimColor on DrawerLayout | Black at 60% opacity
```
- https://m3.material.io/components/bottom-sheets/specs:
```
On Android platforms, the scrim color and opacity is automatically handled by the system UI.
```

**Expected behavior:**
- https://m3.material.io/styles/elevation/applying-elevation:
No change.
```
Scrims use the scrim color role at an opacity of 32%.
```
- https://m3.material.io/components/navigation-drawer/specs:
md.ref.palette.neutral-variant20 -> md.ref.palette.neutral-variant0 (BLACK)?
0.4 -> 0.32
```
Navigation drawers scrim color md.ref.palette.neutral-variant0
Navigation drawers scrim opacity 0.32
```
- https://github.com/material-components/material-components-android/blob/master/docs/components/NavigationDrawer.md:
60% -> 32%
```
Element | Attribute | Related method(s) | Default value
Color | N/A | setScrimColor on DrawerLayout | Black at 32% opacity
```
- https://m3.material.io/components/bottom-sheets/specs:
Remove or revise the description (at least, the scrim opacity can be changed (https://github.com/material-components/material-components-android/commit/f3e4439ca69f993baa6626ad6a82937c2d283155)).
```
On Android platforms, the scrim color and opacity is automatically handled by the system UI.
```

**See also:** https://issuetracker.google.com/issues/365245820

Compare the referenced Material 3 elevation, navigation drawer, and bottom-sheet specifications with docs/components/NavigationDrawer.md. Start by checking the current scrim color and opacity wording in those documentation sources, then update the affected documentation so the stated values and bottom-sheet behavior are consistent; verify all referenced scrim descriptions afterward.

Written by the indexing model from the issue text.